Process for the elimination of phosphorus from pig iron



, basic refining-processes in verter or in the Patented Nov. 22, 1927.

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rumou scnmzox, or uuusrnn, enmity, assrenon r0 vniinmrern s'rannwnan mmnensannscnarr, :oussnnnoam PROCESS FOR THE ELIMINATION- OF PHOSPHORUS FBOM PIG IRON. A

No Drawing. Application filed December 24, 1925, Ser1a1 lie-77,614, and in The elimination of phosphorus from pig, iron is generally effected simultaneously with the elimination of the carbon by the the Thomas-con- Siemens-Martin furnace.

It is however also possible to withdraw the phosphorus from the-pig iron without d1-' minishing the quantity of carbon.

It is known since the seventieth of the last phosphorus from the liquid pig iron 1nto the slag by having oxidizing agents acted upon the pig iron in th presence of slags of a highly basic character vat temperatures which are not essentially higher than those at which thepig iron is smelting. By this 1 process the carbon is not-oxidized, and the formation of carbon oxide only begins when the temperature has arisen. uring the combustion of the carbon the oxidation 0 the phosphorus is stopped and does not recommence before the carbon is com letely eliminated 'from the metal bath. is behaviour is in conformity with the experiences which have been made later on at the Thomas-process. At these low temperatures the phosphorus is split up in a remarkabliy quick manner (compare Ledebur, Han buch der Eisenhiittenkunde, 4th edition, page 696). These facts are confirmed by the observations made at the Htisch-prooes, in thefirst phase of which use is made of the possibility of dephosphorizing the iron in the presence of lime at temperatures somewhat above the smelting-point of pig-iron (compare Fr. Springorum, dissertation Aachen 1910).

invention consists in a process at which, without employing elementary o gen or ores consist of.oxides,-use is m e of the capability of e. carbon-oxide to disengage its oxygen-by a s ial treatment under simultaneous form tion of carbides.

In the metallurgi v hemistry of the iron equilibriums and reversible reactions have a great im rtance. Small changes of. temperature or of concentration. of the substances taking part in the reactions are often sufficient to reverse the normal reaction. Experiments have shown that the iron in the liquid state reacts withcarbon oxide forming soluble carbideand partially soluble fer century that it is possible to transfer the.

Gel-many September ;1, 1924. rous oxide, corresponding the following equation:

' (1) 4Fe +CO:Fe C +FeO.

Low temperatures favour the formation of the substances standing on the right-hand side of the equation and higher ones those of v theIeft-hand side of the equation; growing pressures of carbon oxide change the equi-. libriums towards the right-hand side.

In a corresponding manner the reaction between iron phosphide and carbon oxide according to the following equation:

(2) 600 13Fe 2Fe,P:6Fe C Fe(PO is also reversible, and with this reaction the as the equilibrium mentioned above. Especially the admixture of lime favours the f right-hand side, since by its addition nonreducible tertiary calcium phosphate is formed, which diminishes the concentration of the iron metaphosphate and the tendency of the formation of ironphosphide. At temperatures somewhat above the point at which equilibrium is'influenced in the same sense the presence of lime. At these temperatures iron phosphide is a more eflicient reducing agent for carbon oxide than the liquid metal. At higher temperatures these reactions occurin a different manner. Or -with other words: With corresponding concentrations of the reacting substances iron carbide will reduce more vigorously ferrous oxide than tertiary phosphate. Of course the oxidizing energy of;z the carbon oxide increases with it's partial pressure.

By th ,t formed k ltaneously so far as the cordance with the equihbrinms. tion 1 proceeds onl of iron carbide is ormed, whereas the reaction 2 does not stop at an equilibrium because the metaphosphates are transformed in the nascent state into substances which hinder the inverse reaction.

' The reaction of the carbon oxide is in both cases an exothermic one and sets free,

p The reacuntil a" certain quantity v quantity of heat which amounts to 3710 calories per kg. phosphorus, that is to sa it amounts to about two-thirds of that lieat which is won by the phorus with oxygen.

The technical accomplishment of the invention is effected by blowing carbon oxide gas in a Thomas-converter under admixture of lime orother basic materials. Instead of employing pure carbon-oxide it is also possible to use industrial gases rich in carbonoxide, such as producer gases or blast-furnace gases. It is also possible to employ other devices which are suitable for the reaction of liquid pig iron, lime and carbonoxide.

What I claim and desire to secure by Letters Patent of the United States is 1. A process for the elimination of phosphorus from pig iron without a previous blowing of the pig iron with air, whlch comprises bringing the pig iron into simultaneous combustion of phosreaction with carbon monoxide and basic materials.

'2. A process for the elimination phorus from pig iron without a blowing of the pig iron with air, which comprises bringing the pig iron into simultaneous reaction with gases rich in carbon monoxide and basic materials.

3. A process for of phosprevious the elimination of phosphorus from pig iron without a previous blowing of the pig iron with air, which comprises bringing the pig iron into simultaneous reaction with carbon monoxide and basic materials at a temperature not essentially higher than the melting-point of pig iron.

4. process for the elimination'of phosphorus from pig iron without a previous bld'wing of the pig iron with air, which comprises bringing the pig iron into a Thomas converter under simultaneous blowing in carbon monoxide and addition of lime.

Paor. DR. SCHENCK. 

